Enable/Disable Templates

### The required feature described as a wish

After working more extensively with ACS, I’ve noticed several missing features that are necessary for effective template management.

When uploading a modified version of an existing template (for example, Rocky9), we are forced to give it a new name rather than following our established naming scheme, in order to avoid confusion with the old version. We also cannot simply delete the old template, as it is already in use by multiple production instances.

As a result, an Enable/Disable feature is needed. This would allow older templates to be disabled while keeping updated or approved templates active. Existing instances would continue running on the old templates, while new instances would be created using the enabled, updated ones.

未指定任何文件、测试或入口点；先跟踪 ACS 模板上传和实例创建流程。定义并验证启用/禁用行为，确保现有实例保留其模板，而新实例仅选择已启用的模板。

由索引模型根据 Issue 内容生成。